This application relates to the digital image processing arts. More particularly, the application relates to a method and apparatus for acquiring data from a document to be reproduced by scanning, with suppression of data from the background region thereof in the scanning operation. In certain instances, removal of the background data is highly desirable for purposes of improving the clarity of the digital image and the printed output version of same. Specifically, the present invention provides new and improved methods and apparatus for obtaining the background data from the original input document in the scanning process, wherein the user is able to select one of a plurality of different background suppression data acquisition modes which provide varying levels of background suppression quality and document reproduction speed.
The digital reproduction of a printed document, whether it contains text, continuous tone data, halftone images, and/or any other printed matter, requires the original document to be scanned and converted into digital data. Frequently, the original document will include a background region which is shaded, colored, flecked, or includes other miscellaneous marks thereon which are not intended to be a part of the image information contained in the document. In many instances, it is acceptable to simply reproduce this background data. However, in certain other instances, if this background region is not suppressed during the document reproduction process, the quality of the resulting digital image may be undesirably affected. For example, while a colored background may be aesthetically pleasing in an original document, a monochromatic reproduction of same may be difficult to read due to the resulting non-white background. Therefore, in this instance and many others, it has been deemed highly desirable to suppress the data contained in the background region of an original document for purposes of producing a reproduction of the original document with no background data or noise.
Digital image background suppression methods are widely known. An example of a suitable method is disclosed in U.S. Pat. No. 5,157,740 entitled "Method for Background Suppression in an Image Data Processing System" and assigned on its face to Unisys Corporation. Another example of a background suppression method and apparatus is found in U.S. Pat. No. 3,652,791 entitled "Circuitry for Distinguishing Between Background and Intelligence Areas on a Document" and assigned on its face to Xerox Corporation. The disclosures of U.S. Pat. Nos. 5,157,740 and 3,652,791 are expressly incorporated by reference herein. Digital image processing systems employing background suppression capabilities have not heretofore allowed a user to control the background data acquisition mode so that the user is able to select the appropriate background data acquisition mode depending upon the user's need for high-quality background suppression versus the user's need for high speed document reproduction. That is to say, prior systems allow a user to select only a single background suppression mode, and the single available background suppression mode selected may often be too time-consuming for the user's needs.
For example, prior systems including background suppression capabilities typically require that the entire document be "pre-scanned" for purposes of acquiring the background data from the document. This background data obtained during the "full pre-scan" is fed to a background suppression system which adjusts the document scanning parameters or settings. Then, the full document must be re-scanned with these background suppression settings in place. Obviously, while this full pre-scan approach to obtaining the background data results in a high-quality output image, this mode is very time consuming and often may not be usable due to its detrimental effect on performance, especially given consumer demand for high-speed document reproduction. Other system base the background suppression settings on a portion of the document scanned during the main scanning operation, but do not update the background suppression settings as the main document scanning operation proceeds.
Regardless of the particular background suppression data acquisition mode used by prior digital image processing apparatus/methods, prior systems have not allowed a user to select one of a plurality of different background data acquisition modes as required for a particular document reproduction operation so that the user may select higher quality background suppression or higher speed document reproduction as appropriate to a particular document reproduction job.